Apparatus and method for determination of crimp height

Abstract

The present invention is directed to the accurate and automatic determination of crimp height of a terminal being crimped onto a wire. The crimping apparatus includes a conventional crimping press having a reciprocating ram and base, each carrying a mating half of a crimping die set. A strain gage is arranged to measure crimping forces imposed on the terminal being crimped and a linear sensor measures the position of the ram during the crimping process. As the ram descends and the crimping begins, the force as indicated by the strain gage is monitored until it reaches a predetermined value. Monitoring continues until the force reaches substantially zero, at which time the position of the ram, as indicated by the linear sensor, is translated into crimp height.

I claim: 
     
       1. In a method of determining the crimp height of a terminal crimped onto an element utilizing crimping apparatus which includes a press having a base and a ram arranged for opposing relative reciprocating motion, said base and ram each carrying a mating half of a crimping die set, the steps comprising; (a) placing a terminal and element in crimping position within said crimping apparatus;   (b) causing at least one of said base and said ram to undergo relative motion so, that said die set engages and crimps said terminal onto said element; and   (c) during step (b) determining that the crimping process has actually begun and then monitoring the force imposed on said terminal as said force recedes from a predetermined value to zero, whereupon said force reaching substantially zero, simultaneously therewith determining the distance between the terminal engaging portions of said die set, said distance being said crimp height.   
     
     
       2. The method according to claim 1 wherein said determining that the crimping process has actually begun includes monitoring the force imposed on said terminal as the force reaches a desired value. 
     
     
       3. The method according to claim 2 wherein said crimping apparatus includes means for generating both a force signal indicative of said force imposed on said terminal and a distance signal indicative of said distance between the terminal engaging portions of said die set, wherein step (c) includes: (C1) comparing said force signal to a first reference signal that represents zero, and   (C2) when said force signal is substantially equal to said first reference signal, comparing said distance signal to a second reference signal that represents a desired crimp height and if the difference between said signals exceeds a predetermined amount, generating a reject signal.   
     
     
       4. The method according to claim 3 wherein said crimping apparatus includes a memory and (C2) includes storing said force signal into said memory. 
     
     
       5. The method according to claim 4 including: step (d) translating said distance signal into human readable format. 
     
     
       6. In a machine for crimping a terminal onto an element including a press having a base and a ram arranged for opposed relative reciprocating motion, said base and ram each carrying a mating half of a crimping die set, apparatus for determining the crimp height of a terminal crimped onto an element comprising:   (a) force means for determining and monitoring the force imposed on said terminal during crimping thereof; and   (b) distance means for determining the distance between the terminal engaging portions of said die set when said determined force is substantially equal to zero.   
     
     
       7. The machine according to claim 6 wherein said distance means comprises a linear differential transformer having a stator, an armature, and means for generating a first signal indicative of the relative position of said stator and armature, wherein one of said stator and armature is attached to said base and the other is attached to said ram. 
     
     
       8. The machine according to claim 7 wherein said force means is arranged to generate a second signal indicative of the force imposed on said terminal during said crimping thereof and continuously comparing said second signal to a reference signal indicative of zero until said second signal is substantially equal to zero. 
     
     
       9. The machine according to claim 8 wherein said force means is a strain gauge and wherein said machine includes means for communicating said distance to an operator.